The present invention relates to a displaying apparatus for a vehicle which assures that the displayed image for displaying informations on the present running state of the vehicle such as a running speed or the like is visually recognized by a driver by reflecting the displayed image appearing on the screen of a displaying unit to an eye range disposed on the driver's seat side.
A displaying apparatus for a vehicle for displaying a displayed image on the screen of a displaying unit from a remote location by utilizing a reflective plate so as to increase a visual recognizing speed with the vehicle has been hitherto known.
The foregoing type of displaying apparatus for a vehicle as mentioned above shows an excellent effect for displaying a certain displayed image from a remote location as the length of light beam path for allowing light beam to pass along the light beam path via reflection is elongated more and more. In view of the foregoing fact, proposals have been made with respect to a displaying apparatus of the foregoing type wherein the whole displaying apparatus is compactly designed with a reduced space to be occupied by the reflected light beam path, and moreover, the total length of light beam path is elongated.
FIG. 4 is a side view of a conventional displaying apparatus for a vehicle which schematically shows by way of example the structure of the apparatus.
In FIG. 4, reference numeral 11 designates a meter hood portion of a dashboard, reference numeral 21 designates a self-illuminating type displaying unit such as a liquid crystal displaying unit, a fluorescent displaying tube or the like disposed in the dashboard to display informations on the present running state of the vehicle such as a running speed or the like, reference numeral 21a designates a surface glass disposed on the displaying surface side (displaying light beam emitting side) of the displaying unit 21, and reference numeral 31 designates a first reflective plate having light permeability disposed on the displaying surface side of the displaying unit 21. The first reflective plate 31 is molded of a transparent acrylic resin having, e.g., a smoked/darkened color.
Reference numeral 41 designates a second reflective plate which is located opposite to the displaying unit 21 with the first reflective plate 31 being interposed therebetween. The second reflective plate 41 serves to fully reflect the displaying light beam to the first reflective plate 31.
Reference numeral 51 designates an eye range which is disposed on the driver's seat side so as to allow a displayed image on the displaying unit 21 to be visually recognized by a driver, reference numeral 51U designates an upper limit of the eye range 51 from which the lower end of the second reflective plate 41 appearing on the first reflective plate 31 can be seen, reference numeral 51C designates a center of the eye range 51, and reference numeral 51D designates a lower end of the eye range 51 from which the upper end of the second reflective plate 41 appearing on the first reflective plate 31 can be seen.
Reference character A.sub.S designates a visually recognizable area. The visually recognizable area A.sub.S is defined by a first line L.sub.1 extending between the upper limit 51U of the eye range 51 and the lower end of the second reflective plate 41 appearing on the first reflective plate 31, a second line L.sub.2 extending between the lower limit 51D of the eye range 51 and the upper end of the second reflective plate 41 appearing on the first reflective plate 31, and the second reflective plate 41 appearing on the first reflective plate 31.
Reference character A.sub.S1 designates a visual recognizable area. The visually recognizable area A.sub.S1 corresponds to the visual recognizable area A.sub.S of the second reflective plate 41.
Reference characters X and X.sub.1 designate displayed images. The displayed image X is visually recognized by a driver from the eye range 51 at the position located behind the first reflective plate 31, and the displayed image X.sub.1 is coincident with the displayed image X appearing on the first reflective plate 31.
Reference characters X.sub.11 to X.sub.13 designate ghosts (virtual images) which are derived from a surface glass 21a on the displaying unit 21, the first reflective plate 31 and the second reflective plate 41.
Reference characters 32a and 32b designate light masking members which are disposed on the displaying unit 21 side of the first reflective plate 31. The light masking members 32a an 32b serve to mask the first reflective plate 31 therewith with the exception of a range A.sub.0 where displaying light beam of the displaying unit 21 is directed to the second reflective plate 41, whereby the displaying unit 21 can not visually be seen from the eye range 51 by any means.
Next, a mode of operation of the conventional displaying apparatus constructed in the aforementioned manner will be described below.
First, displaying light beam emitted from the displaying unit 21 to display a displayed image passes through the first reflective plate 31, and subsequently, it is reflected at the second reflective plate 41.
The reflected light beam fully reflected at the second reflective plate 41 is reflected again to the eye range 51 via the first reflective plate 31.
With such construction, when the first reflective plate 31 is seen from the eye range 51, the displayed image X is visually recognized by a driver as a virtual image in the visual recognizable area A.sub.S located behind the first reflective plate 31.
Since the displayed image X visually recognized in that way is displayed at the remote position corresponding to a length of light beam path within the range defined by the second reflective plate 41 appearing on the first reflective plate 31, image displaying can be achieved with excellent visual recognizability.
Since the conventional displaying apparatus for a vehicle is constructed in the above-described manner, a part of the displaying light beam reflected from the second reflective plate 41 to the first reflective plate 31 permeates through the first reflective plate 31 again so that it is irradiated to the surface glass 21a of the displaying unit 21. Thus, the displayed image X.sub.1 is transformed into a virtual image X.sub.11 due to reflection at the surface glass 21a.
Subsequently, the virtual image X.sub.11 is reflected at the second reflective plate 41 in the enlarged state to become a virtual image X.sub.12 which in turn is reflected at the first reflective plate 31, causing a virtual image X.sub.13 to be located in the visual recognizable area A.sub.S.
Consequently, as shown in FIG. 5, since the virtual image (ghost) X.sub.13 is visually recognized together with the displayed image X from the eye range 51 in the visual recognizing area A.sub.S, there arise malfunctions that display quality-of the displayed image X is reduced, and moreover, visual recognizability of the displaying apparatus is degraded (with reduced optical contrast).
Although the virtual image X.sub.13 can be located at the visual recognizing area A.sub.S by reducing the light permeability of the first reflective plate 31, there arise another malfunctions that the displaying unit 21 is illuminated with reduced brightness and an efficiency of the displaying apparatus is reduced, resulting in the displaying apparatus being fabricated at an expensive cost because of a necessity for improving the brightness of the displaying unit 21.
In addition, another malfunction is that when the displaying unit 21 is displaced in the upward direction in order to design the displaying apparatus with smaller vertical dimensions, the displaying unit 21 can unavoidably be seen from the eye range 51.